major service and backfiring remedies

[dolphaxel]

So my 2003 m800sie is due for its 12k major service and that getting done, but an ongoing issue ive had with this bike since the day it came into my possession is a backfire through the intake occasionally. Come around a low speed corner and lightly roll into the next gear and "pop". Its always done it, but it seems closer to its service intervals it gets worse. The last few times i rode it before the service it was terrible. if you werent on the gas or trying to hold steady "pop pop pop" down the road. when I pulled the covered and took all the measurements I found the intake opener almost zip for clearance. I should mention that the backfiring doesnt happen until its usually above 150*. I corrected that gap and buttoned it back up. Instant improvement, but not gone. I think Im going back in, but I wanted some advice. All of my closers are at the high end of the limits. Would reducing those possibliy help on the intake issues? Im going to pull the belts this time so I can et them tighter and make sure they dont bind. I feel like I'm making headway on the issue since the problem seemed to vastly improve with that simple adjustment. Ive also read some place that folks are using slightly different clearance numbers? any how A couple more days till the belts and harmonic tool make it and this time I'm going in for battle!

[Speeddog]

What clearance numbers are you using?

[jduke]

Good suggestion and also check your TPS.

[dolphaxel]

the clearance numbers I have are out of my shop manual. it says openers are .10-.15mm and 0-.05mm for closers. I have the openers currently on the tighter side of that range and the closers are near to the loose side of that. I may loosen up the openers a bit on the intake valves and try for a little tighter on the closers. I am gonna pull the belts off next go around for replacement anyway. I will admit a little paranoia about getting the closers too tight.

What clearance numbers are you using?

[Speeddog]

Closers as near to zero as you can get without binding, openers .004" on intakes, .005" on exhaust.

[dolphaxel]

oh boy. thats gonna take some work and probably a bit of shim ordering. Ive got the shim kit, but since they are all about even now i'm gonna need a bunch of the same likely. How do you feel about sanding of shims? I've read and seen people do it. just fine paper on glass. Do you usually do valves with the belts off?

[EEL]

Other option that I've used to cheat the system is to buy MBP retainers on the closers. They usually add some clearance back and they are a good long term investment.

[ducpainter]

oh boy. thats gonna take some work and probably a bit of shim ordering. Ive got the shim kit, but since they are all about even now i'm gonna need a bunch of the same likely. How do you feel about sanding of shims? I've read and seen people do it. just fine paper on glass. Do you usually do valves with the belts off?

You really can't verify that the closers aren't too tight with the belts on, so it makes sense to remove them.

Also, you should adjust closers and then recheck the opening clearance...they often change.

Sanding works. I wouldn't try to sand .010 off, but a couple of thousandths works. Use a figure eight and rotate the shim in your fingers to keep it square.

[EEL]

You really can't verify that the closers aren't too tight with the belts on, so it makes sense to remove them.

Also, you should adjust closers and then recheck the opening clearance...they often change.

Sanding works. I wouldn't try to sand .010 off, but a couple of thousandths works. Use a figure eight and rotate the shim in your fingers to keep it square.

One important screwup a lot of people make. They use a something flat to sand on (like a piece of glass) but they dont make sure that what they are sanding on is LEVEL.

This will get you better results

[Cloner]

One important screwup a lot of people make. They use a something flat to sand on (like a piece of glass) but they dont make sure that what they are sanding on is LEVEL.

This will get you better results

That might be the silliest thing I've ever heard.  Why in hell does it matter whether or not the flat surface is level when you're lapping by hand?  My hand certainly isn't "level".  Who gives a shit as long as the surface is flat and your hold the shim as close to perpendicular as possible?  I use a figure 8 motion to lap them down to try to sand as evenly as possible....but "level"?   

[dolphaxel]

alright. spent some serious time plying with the valves and I think everything is in order there. What a pain in the ass!! well maybe I'm just not that great at it, but it takes me quite a bit of time. the belt swap took me only about 2 minutes, but there are some major discrepancies on tension. I currently have them at 110hz as recommended by the packaging on the ca cycles works belts, but my manual says very different. it says 145 horz. 160 vert. That seems really freaking tight, but what do I know. I dont really want to tighten them that much when the belts say 110 max. Any thoughts on whats best here? for the record the ones put on at the dealer 2 years and 3k ago were about loose enough to fall off!

[EEL]

That might be the silliest thing I've ever heard.  Why in hell does it matter whether or not the flat surface is level when you're lapping by hand?  My hand certainly isn't "level".  Who gives a shit as long as the surface is flat and your hold the shim as close to perpendicular as possible?  I use a figure 8 motion to lap them down to try to sand as evenly as possible....but "level"?  

I've been doing this for ten years man. Experience has taught me a few things. In order to sand, you need to apply some pressure to the shim. When you're talking about thousandths of an inch. Our human hands cant adjust for the varying slope and the shim gets more sanded on one side than the other (even if you are rotating it, doing figure 8's, whatever)

If what you are saying is right, put your flat surface at a 60 degree angle and see what happens. I would rather spend 2 minutes leveling the sanding surface than spend 2 days waiting for another shim.

If you're superhuman precise, congratulations, go get yourself a cookie as most of us are not. Otherwise go say "serenity now" 10 times, get a a beer and RELAX

[EEL]

alright. spent some serious time plying with the valves and I think everything is in order there. What a pain in the ass!! well maybe I'm just not that great at it, but it takes me quite a bit of time. the belt swap took me only about 2 minutes, but there are some major discrepancies on tension. I currently have them at 110hz as recommended by the packaging on the ca cycles works belts, but my manual says very different. it says 145 horz. 160 vert. That seems really freaking tight, but what do I know. I dont really want to tighten them that much when the belts say 110 max. Any thoughts on whats best here? for the record the ones put on at the dealer 2 years and 3k ago were about loose enough to fall off!

Its 110 max. I would stick to 100 - 105. Dont do 140, you'll screw up your pulleys

[GreasySnipe]

One important screwup a lot of people make. They use a something flat to sand on (like a piece of glass) but they dont make sure that what they are sanding on is LEVEL.

This will get you better results

I use a lapping plate like this one:

[ducpainter]

I've been doing this for ten years man. Experience has taught me a few things. In order to sand, you need to apply some pressure to the shim. When you're talking about thousandths of an inch. Our human hands cant adjust for the varying slope and the shim gets more sanded on one side than the other (even if you are rotating it, doing figure 8's, whatever)

If what you are saying is right, put your flat surface at a 60 degree angle and see what happens. I would rather spend 2 minutes leveling the sanding surface than spend 2 days waiting for another shim.

If you're superhuman precise, congratulations, go get yourself a cookie as most of us are not. Otherwise go say "serenity now" 10 times, get a a beer and RELAX

After you get the sanding surface level...

do you put some sort of device on your wrist to make certain you don't apply more pressure to the right or left?

It's a question.